An object of the present invention is to improve upon a laser spark plug and a cleaning method of the aforementioned type in such a way as to enable an efficient cleaning, in particular of the combustion chamber window of the laser spark plug.
This object may be achieved with a laser spark plug of the aforementioned type according to the present invention in that the laser spark plug, in the area of the component, includes at least one channel which has at least two orifice sections and allows fluid communication between the orifice sections, a first orifice section being situated in the area of an outer surface of the combustion chamber window and a second orifice section being situated in a radially outer area of the laser spark plug, particularly of the component.
The channel according to the present invention allows for the particularly advantageous application of fluid, for example, a cleaning solution or the like, to the outer surface of the combustion chamber window. The channel according to the present invention further advantageously allows a targeted introduction of the cleaning fluid into the area of the laser spark plug to be cleaned.
In one advantageous specific embodiment it is provided that a longitudinal axis of at least one longitudinal section situated in the area of the first orifice section points essentially at a radially inward lying area of an outer surface of the combustion chamber window which allows a targeted introduction of a cleaning fluid onto the optically active area of the combustion chamber window, regardless of the spatial configuration of the second orifice section of the channel. This means that a flow direction of a cleaning fluid introduced by the channel may be advantageously determined or influenced by the longitudinal axis of the first longitudinal section, in particular its orientation.
According to one further specific embodiment it may be particularly advantageously provided that the longitudinal axis of the first longitudinal section is oriented in such a way that a point of intersection of the longitudinal axis with the outer surface of the combustion chamber window includes a distance relative to the optical axis of the laser spark plug, which amounts to at least 20%, which may be at least 40%, of a radiation cross section of the laser radiation in the area of the outer surface. Based on tests conducted by the applicant, this configuration allows for a particularly efficient cleaning of the outer surface of the combustion chamber window in the surface area through which the laser radiation provided by the laser spark plug passes into the exterior.
In one further advantageous specific embodiment it is provided that at least one second longitudinal section of the channel has a diameter of from 0.5 mm to approximately 4.0 mm, in particular from approximately 1.0 mm to approximately 2.0 mm.
This channel configuration allows for an optimal application of pressurized cleaning fluid to the combustion chamber window, the cleaning fluid being capable of being injected, in particular, at a relatively high pulse (high pressure, high speed) onto the combustion chamber window and thereby cleaning the latter. In addition to applying highly pressurized cleaning fluid to the combustion chamber window, a wetting with cleaning fluid, at, for example, relatively low pressure, is also advantageously possible via the channel according to the present invention. Alternatively or in addition, a mechanical cleaning through the channel may also be carried out, for example using a brush or a cotton swab or the like.
In one further advantageous specific embodiment it is provided that a first longitudinal section of the channel situated in the area of the first orifice section has a diameter of from approximately 0.1 mm to approximately 2.0 mm, in particular from approximately 0.2 mm to approximately 1.0 mm.
If the channel according to the present invention includes, for example, different longitudinal sections, each with different cross-sectional openings or diameters, a jet effect for a cleaning fluid flowing through the channel may advantageously be achieved, thereby allowing the pulse of the cleaning agent flow to be advantageously influenced.
In one further advantageous specific embodiment, the channel is configured in such a way that it may be temporarily closed so that no fluid communication is possible between the first and the second orifice section. For example, the channel may at least in sections advantageously include an internal thread, into which a set screw may be screwed in order to prevent fluid communication between the orifice sections of the channel according to the present invention.
The channel may be particularly advantageously configured at least in sections as a stepped bore, making it possible to manufacture the laser spark plug according to the present invention particularly cost-effectively. Generally, however, the channel according to the present invention may also have a geometry of greater complexity. In particular, the channel does not necessarily have to be essentially cylindrical in shape, rather it may, for example, also include one or multiple curved longitudinal sections which make it possible to change the direction of the cleaning fluid. It is also conceivable, for example, to provide the second orifice section into which the cleaning fluid to be applied to the combustion chamber window is to be introduced, in an axial end area of the laser spark plug which faces away from the combustion chamber, whereby a cleaning fluid would also be introducible, for example, in an installation state of the laser spark plug into a cylindrical shank of an internal combustion engine.
In one advantageous specific embodiment, the laser spark plug includes a fastening arrangement in a radially outward area for mechanical connection to a target system, in particular an external thread for screwing into a corresponding internal thread of a cylinder head of an internal combustion engine. In this configuration according to the present invention, the second orifice section of the channel according to the present invention may be situated particularly in the area of the fastening arrangement in such a way that the second orifice section is closed off when the laser spark plug is installed in the target system. This advantageously ensures that in the installation position of the laser spark plug, the second orifice section situated radially on the outside of the laser spark plug is not directly connected to a combustion chamber of the internal combustion engine into which the laser spark plug projects in its installation position.
Alternatively or in addition, the channel may, as previously described above, be closed off with the aid of an appropriate closure arrangement such as, for example, a set screw.
According to one further advantageous specific embodiment, the component which surrounds at least part of the beam path of the laser radiation is configured, for example, as a diaphragm and/or a prechamber. In both cases, the relevant component impedes access to the outer surface of the combustion chamber window so that it is particularly advantageous to use the channel according to the present invention for cleaning the combustion chamber window. Advantageously, the channel may be integrated, at least in part, into the diaphragm or the prechamber wall.
A further approach to the object of the present invention is provided by a method as described and disclosed herein.
Further advantageous embodiments are the subject matter of the descriptions herein.
Additional features, applications and advantages of the present invention result from the following description of exemplary embodiments of the present invention represented in the figures of the drawing. All features described or represented herein form, by themselves or in any arbitrary combination, the subject matter of the present invention, regardless of their subsumption in the patent claims or their back-reference, and regardless of their wording or representation in the description or in the drawings.